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Reply-To: moss AT cs DOT umass DOT edu
Subject: Re: fork() fails if it is called recursively from a child thread.
References: <20170309203959 DOT 1e7e32d20bf7ec06c705d3ba AT nifty DOT ne DOT jp>
To: cygwin AT cygwin DOT com
From: Eliot Moss <moss AT cs DOT umass DOT edu>
Message-ID: <882e88d5-d508-fee8-e22c-47434297e8c8@cs.umass.edu>
Date: Thu, 9 Mar 2017 08:53:19 -0500
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On 3/9/2017 6:39 AM, Takashi Yano wrote:
 > Hello,
 >
 > I found fork() fails if it is called recursively from a child thread.
 >
 > Simple test case, attached (fk.c), reproduces this problem.
 >
 > Expected result:
 > Parent 0 [22034] exit.
 > Child 0 [22036] works.
 > Parent 1 [22036] exit.
 > Child 1 [22038] works.
 > Parent 2 [22038] exit.
 > Child 2 [22039] works.
 > Parent 3 [22039] exit.
 > Child 3 [22040] works.
 > Parent 4 [22040] exit.
 > Child 4 [22041] works.
 >
 > Result in cygwin 2.7.0:
 > Child 0 [4668] works.
 > Parent 0 [7188] exit.
 >       0 [main] a 4668 fork: child -1 - forked process 8456 died unexpectedly, retry 0, exit code 
0xC0000142, errno 11
 > fork(): Resource temporarily unavailable
 >
 > Strictly speaking, the test case is not safe because it calls functions
 > which are not async-signal-safe from forked child process, i.e. printf()
 > and perror(), in spite of multi-thread. However the same happens even
 > without printf() and perror().
 >
 > This is the cause of which iperf 2.0.5 with option -s -D fails to start
 > as daemon.
 >
 > Is this the known issue?

This strikes me as either BLODA (interfering software) or a need to
rebase some dll(s).  That's what I most commonly see that causes that
fork error.

Regards - Eliot Moss

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